Portion of the invention described herein was also described in patent application no. 09/681,123, filed. Jan. 15, 2001, now abandoned.
(1) Field of the Invention
1. The present invention relates to the use of solar energy for conversion of solar energy to electrical and thermal energy with the added function of radiant cooling for general use with industrial/commercial processes requiring working fluid cooling; and using a heat transfer plate to heat a photovoltaic array to maintain its operating temperature in a range that provides maximum efficiency to improve electrical energy conversion in cold climates or winter conditions.
(2) Description of the Related Art
2. The conversion of solar energy to thermal or electrical energy through the use of systems such as photovoltaic arrays, passive absorbers of solar energy, solar furnaces, trough concentrating collectors with sun trackers is well established in the art. U.S. Pat. No. 4,315,163 describes a multipower electrical system for supplying electrical energy to a house including a solar photovoltaic array, a battery charger and DC to AC inverter. U.S. Pat. No. 4,147,157 describes an active solar energy system comprising an array of solar collectors for both generating power for a pump; and for heating a fluid, a pumping device powered by the array to circulate the heated fluid and a storage tank to contain the heated fluid. Similarly, U.S. Pat. No. 5,293,447 describes a system for heating water using solar energy comprising a photovoltaic array, a water heater and a controller.
3. Systems have also been proposed for simultaneously converting solar energy to thermal and electrical. For example, U.S. Pat. No. 4,392,008 describes a flat plated solar thermal collector below and in spaced conductive relationship to a plate-mounted array of photovoltaic cells. U.S. Pat. No. 5,522,944 describes an apparatus with an array of photovoltaic cells and a plurality of interconnected heat collecting tubes disposed on the same plane with the array.
4. Other systems attempting to optimize electrical energy conversion and provide conversion to thermal energy from solar energy have been proposed. For example, U.S. Pat. No. 4,373,308 describes a solar cell array consisting of individually relatable, elongated segments driven by a sun tracker and motor with a thermal solar collector supported beneath the solar cell array for utilization of solar energy received through a roof opening in a building. U.S. Pat. No. 6,018,123 describes a solar cell module provided at the position of a heat collecting plate inside a heat collector in which hot air can be led into a house while maintaining the performance of solar cells.
5. However, there is an unmet need in the art for improvements to optimize systems that convert solar energy to both thermal and electrical energy efficiently in colder climates adding a function to radiate heat to cool fluids and keep the collectors free of snow and ice.
6. The invention provides enhanced performance characteristics and adds a heat radiator function within a single enclosure that previous inventions do not provide.
7. Included within a single enclosure is a photevoltaic grid that converts solar energy into electrical energy, a thermally conductive heat transfer plate disposed on a plane below the photovoltaic grid. The heat transfer plate converts the solar energy in thermal energy uniformly distributed over the entire plate. On a plane below the plate but thermally coupled to the plate by a thermal conductive compound are copper tubes which impart the thermal energy from the plate to a fluid disposed inside the tube heating the fluid to a high temperature before being discharged from the enclosure.
8. In a radiator mode, a hot fluid is introduced to the copper tubes that absorb the heat form the fluid, cooling the fluid. This thermal energy is conducted from the tubes to the heat transfer plate that radiates the thermal energy through the photovoltaic grid and out through the glass covered top of the enclosure.
9. The capability to convert solar energy to electrical energy and to thermal energy is improved by the addition of a Fresnel lens array supported above the photovoltaic grid by lens support panels riveted to the enclosure. The Fresnel lens magnifies the amount of insolation (solar energy) received by the photovoltaic grid and the thermal transfer plate.
The Fresnel lens is held in place on the lens supports by lens retainer in a manner that imparts a curvature to the lens. This curvature allows the lens to magnify the available insolation regardless of the Sun""s position providing a passive solar tracker capability. Thus the need for a Sun tracker sensor, drive electronics and a drive motor coupled to the lens array is not required, saving energy, weight and cost. Testing has shown that the performance of the photovoltaic grid is improved by at least 14 percent using this lens feature.
10. The ability to remove heat from a hot fluid and radiate the heat through the photovoltaic grid and out the enclosure top heats the lens array and the surrounding lens support panels. This heating ability allows operation of the collector in cold climates preventing the build up of ice and snow on the collector.
11. A temperature sensor is provided so that when the sensor output signal is coupled to a microprocessor-based controller, thermostat or Proportional-Integral-Derivative (PID) controller, fluid flow rate can be regulated as a function of its discharge temperature. By this method, fluid discharged from the collector can be maintained at a constant temperature. Since this temperature is also proportional to the photovoltaic grid temperature, the photovoltaic operating temperature can maintained within the preferred range of 70xc2x0 F. to 100xc2x0 F. which is the range where the photovoltaic grid is most efficient.
12. Another benefit is provided with the flow of cold fluid through the collector panels, if mounted on a building roof, reduces the roof temperature in the immediate area around the panel enclosure from roof temperatures of 100xc2x0 F. to 140xc2x0 F. down to 80xc2x0 F. to 120xc2x0 F. depending upon the building environmental conditions. This ability to cool roofs augments or replaces building air conditioning thus providing a savings in building air conditioning costs.